This paper developed an understandable economic mathematical model of total cost of quality related to the use of control chart. This model considers both statistical quality and cost criteria. The statistical quality constraints considered in this paper are type I error (α) and type II error (β). The total cost of quality is a function of sample size (n) and sampling frequency (f). The model of total cost can be optimized to determine values of n and f that minimize the total cost of quality, while quality level is satisfied. The model can be solved by common spreadsheet program. The economic statistical model is developed under the real situation of a case study company to make the model realistic.